Such winches have for some time been provided with a plurality of drive ratios between their drive input and the winch drum and various arrangements have been proposed for allowing interchange between various drive ratios, this interchange being achieved, at least in all the more recent developments, automatically upon reversal of the direction of the drive input, without further manual interference.
There are two sorts of winch to which this interchange is applied.
In a first sort the first speed ratio, the ratio of lowest mechanical advantage to the user, is a 1:1 drive achieved by direct action between a handle and the drum (U.S. Pat. No. 3728914) or through a pawl and ratchet drive one side of which is associated with the drum and the other side of which is associated with the drive shaft (for example, U.S. Pat. No. 3973755).
In a second sort, all the speed ratios involve drive transmission through gear trains. In one line of development illustrated by U.S. Pat. Nos. 3145974 and 4054266 automatic change is provided by means of a movably-mounted traveller gear which is engageable between coplanar transmission pinions while they are rotating in one direction but is driven in an orbital motion out of engagement by their rotation in the opposite direction. The proposals seen in U.S. Pat. Nos. 3927580 and 3998431, on the other hand, use axial movements to engage and automatically disengage drive. In U.S. Pat. No. 3927580 drive coupling to one gear is through a dog clutch which is manually urged into engagement but is positively driven out of engagement by face cams moving it axially when drive is reversed. In U.S. Pat. No. 3,998,431, for a special application, a collar is axially movable to interfere with the driving engagement between pawls on a pinion and a ratchet track on the drive shaft, the pinion and ratchet track being both axially stationary.